There are tons of solutions for semi-open wifi for custmers, e.g. Sonicwall or Meraki firewalls and filter rules, etc. Many of them are Out of the Box solution

There are tons of solutions for semi-open wifi for custmers, e.g. Sonicwall or Meraki firewalls and filter rules, etc. Many of them are Out of the Box solutions too, and are plainly advertised as SMB / coffee shop solutions. Set em up, turn on filtering, log stuff, turn over any records if/when law enforcement asks. You could probably hack something together that costs less, but that's adds overhead and wastes time; you need just enough to prove you're doing diligence and keep out of the low hanging fruit. Log everything, and if the fuzz asks for records be able to hand them over.